Polyester film coated in-line with an silane

ABSTRACT

Oriented polyester film primer coated in-line with a hydrolyzed aminosilane is discovered. The aminosilanes in the unhydrolyzed state have the formula: (R1)aSi(R2)b(R3)c wherein R1 is a functional group with at least one primary amino group; R2 is a hydrolyzeable group such as a lower alkoxy group, an acetoxy group, or a halide; and R3 is a nonreactive, nonhydrolyzeable group such as a lower alkyl or a phenyl group; with (a) being greater than or equal to 1; (b) being greater than or equal to 1; (c) being greater than or equal to zero; and with a+b+c=4. The hydrolyzed aminosilane is applied to the film as an aqueous solution at any suitable stage during manufacture of the film, i.e., before, or during, or after the stretching operation, but prior to heat setting the film. The resultant primed polyester film is found to exhibit excellent adhesion to other polymeric materials.

This is a continuation-in-part of application Ser. No. 07/240,701 filedSept. 6, 1988.

BACKGROUND OF THE INVENTION

(1) Field Of The Invention

The present invention relates to oriented polyester film coated in-lineon at least one side with a water soluble primer coating compositioncomprising a hydrolyzed aminofunctional silane which renders the filmmore receptive to extrusion coating with other polymeric film materialssuch as polyolefins.

(2) Prior Art

Oriented polyester film, particularly biaxially oriented film composedof polyethylene terephthalate (PET), has been widely used as a packagingmaterial or as a base for microfilm, reprographic films, proofing films,and the like. It has good optical clarity and toughness which renders itextremely suitable for such applications.

A major use of PET film is in laminations with other polymers and withpaper or foil. Often the PET film is extrusion coated with polyethyleneor an ethylene copolymer in order to get heat sealing capability,adhesion to another material such as aluminum foil, additional bulk(thickness) or stiffness, or to achieve properties not possible with PETalone.

Unfortunately, the surface of PET film is not very receptive toextrusion coating with other polymers. Numerous primer coatings areknown in the prior art for application to the surface of polyester filmto improve the adhesion of the film to various materials. Examples ofsuch coatings include compositions based on vinylidene chloride polymers(U.S. Pat. No. 2,698,240), thermosetting acrylic or methacrylic polymers(U.S. Pat. No. 3,819,773) and like materials. Certain water dispersiblecopolyesters have also been disclosed as adhesives for laminating sheetsof polyester film to one another or to sheets of nylon film, as taughtin U.S. Pat. Nos. 3,563,942 and 3,779,993. More commonly, solvent basedpolyurethane adhesives and polyethyleneimine primers are used withattendant problems with solvent emissions and safety. Corona dischargetreatment is also used with and without a primer to achieve adhesionbetween the extrudates.

In common practice, for extrusion coating, a converter will corona treatthe PET film as received from the manufacturer, primer coat the coronatreated film, dry the primer coat, and then extrusion coat anotherpolymer onto the film (treating film "off" the manufacturing line iscommonly referred to as "off-line", treating film during themanufacturing process is commonly referred to as "in-line"). The need toprime the film introduced an additional process step that requiresexpensive additional equipment and affects yields in off-line treatmentaccomplished by a converter. In addition, if a solvent based primer isrequired, additional safety and pollution equipment is required and anadditional regulatory burden is imposed.

For the above reasons it would be advantageous for the converter to beable to obtain an already treated or primed film that was directlyextrusion coatable without additional priming or corona treatment. Tokeep from incurring the same costs and problems it is also advantageousthat the directly extrusion coatable film be produced by treating orprimer coating the film in-line during the manufacturing of the film.For an in-line process it would be ideal for the primer coating to bewater based for safety and health reasons, reclaimable (i.e., not causeexcessive yellowing or deterioration in physical properties when primercoated film scrap is mixed with fresh polymer and reextruded, which isnecessary for an in-line process because of low conversionefficiencies), and hard enough to allow the film to be wound into a roll(as would be necessary for a directly extrusion coatable film) withoutsticking or blocking.

A directly extrusion coatable polyester film is disclosed in U.S. Pat.No. 4,410,600 to P. T. McGrail. Disclosed is a biaxially oriented PETfilm coated in-line with a crosslinked styrene-maleic anhydridecopolymer. The coated film, however, still requires corona dischargetreatment prior to extrusion coating.

The use of silane coupling agents to improve the bonding properties ofpolyethylene sheets and polyester sheets is known. For example,polyester sheets and polyethylene sheets primed with eithervinyltrimethoxysilane or chloropropyltrimethoxysilane have beensuccessfully laminated using a hot melt adhesive such as anethylene/vinyl acetate terpolymer or an elastomeric polyester asdisclosed by E. Plueddemann, "Bonding Through Coupling Agents", PlenumPress, New York, 1985. In addition, the use ofN-2-aminoethyl-3-aminopropyltrimethoxysilane (sold under the trademarkZ-6020 by Dow Corning) as a primer coating to enhance the adhesion of anionomer resin (salt of a copolymer of ethylene and methacrylic acid) toglass and to polycarbonate sheets is disclosed in U.S. Pat. No.4,663,228. Related silanes such as N-3-aminopropyltrialkoxysilanes areknown to enhance the adhesion between polyurethane films and glasssubstrates, as disclosed in published European patent application No.171,917.

None of these prior art disclosures addresses the problem of directextrusion coatability of film, particularly of polyester film topolyethylene, ethylene copolymers and ionomers, or other polymer films,without additional primers or additional corona treatment.

Accordingly, it is a primary object of this invention to provide aprimer coating which is applied in-line during the polyester filmmanufacturing process.

Accordingly, it is an object of this invention to provide an oriented,polyester film that can be directly extrusion coatable with otherpolymers without the need for additional primers or additional coronatreatment.

Accordingly, it is also an object of this invention to provide apolyester film having a primer coating thereon in which the primercoated film scrap can be reclaimed without causing excessive yellowingor deterioration in properties of the reextruded polymer.

Most prior art primer coatings employ volatile solvents, thus requiringassociated equipment to handle the solvents, associated equipment toprotect the workers, and associated equipment to dispose of any wastesolvent.

Accordingly, it is another object of the present invention to develop anaqueous primer coating that can be incorporated into most existingsystems without the need for expensive associated equipment.

SUMMARY OF THE INVENTION

These and other objects of the invention may now be achieved by theprovision of an oriented polyester film which has been in-line primercoated with a hydrolyzed aminofunctional silane to render the filmreceptive to direct extrusion coating with other polymers.

The aminofunctional silanes useful as a primer for the purposes of thisinvention are represented by the general formula in their unhydrolyzedstate:

    (R.sup.1).sub.a Si(R.sup.2).sub.b (R.sup.3).sub.c

wherein R¹ is a functional group with at least one primary amino group,R² is a hydrolyzeable group such as a lower alkoxy group, an acetoxygroup, or a halide, and R³ is a nonreactive, nonhydrolyzeable group suchas a lower alkyl or a phenyl group; with (a) being greater than or equalto 1; (b) being greater than or equal to 1; (c) being greater than orequal to zero; and a+b+c=4.

Generally, the aminofunctional silane is hydrolyzed in water and appliedto one or more surfaces of the oriented polyester film by anyconventional in-line method such as spray coating or roll coating. Oncethe silane primer coating has dried, the primed polyester film isreceptive to direct extrusion coating with one or more polymers. Theextrusion coating can be conducted by any conventional process. Theprimer coating serves to bond the polyester film to the extrudate, thusforming a laminate.

In the broadest sense, the present invention is directed to an orientedpolyester film having an effective amount of primer coating, appliedin-line, to render the film receptive to direct extrusion coating withone or more polymers; the primer represented in the unhydrolyzed stateby the general formula:

    (R.sup.1).sub.a Si(R.sup.2).sub.b (R.sup.3).sub.c

wherein R¹ is a functional group with at least one primary amino group,R² is a hydrolyzeable group, and R³ is a nonreactive, nonhydrolyzeablegroup; with (a) being greater than or equal to 1; (b) being greater thanor equal to 1; (c) being greater than or equal to zero; and a+b+c=4.

In the broadest sense the present invention is also represented by alaminate having an oriented polyester film, an in-line applied primercoating, and one or more directly extruded polymer(s); the primercoating represented in the unhydrolyzed state by the general formula:

    (R.sup.1).sub.a Si(R.sup.2).sub.b (R.sup.3).sub.c

wherein R¹ is a functional group with at least one primary amino group,R² is a hydrolyzeable group, and R³ is a nonreactive, nonhydrolyzeablegroup; with (a) being greater than or equal to 1; (b) being greater thanor equal to 1; (c) being greater than or equal to zero; and a+b+c=4.

DETAILED DESCRIPTION OF THE INVENTION

Silanes are water soluble or water dispersible after hydrolysis, withaminofunctional silanes being especially water soluble. The presentinventors have found that aminosilanes provide good adhesion ofextrusion coated polymers to polyester film without further priming orcorona treatment so long as the aminosilane primer coating is appliedin-line, i.e., during the manufacturing process. The scrap frompolyester film primed with an aminosilane coating can be reclaimed.

The aminofunctional silanes useful as a primer for the purposes of thisinvention are represented in their unhydrolyzed state by the generalformula:

    (R.sup.1).sub.a Si(R.sup.2).sub.b (R.sup.3).sub.c

wherein R¹ is a functional group with at least one primary amino group,R² is a hydrolyzeable group selected from lower alkoxy group having 1-8carbon atoms, an acetoxy group, or a halide, and R³ is a nonreactive,nonhydrolyzeable group selected from a lower alkyl group having 1-8carbon atoms or a phenyl group; with (a) being greater than or equal to1; (b) being greater than or equal to 1; (c) being greater than or equalto zero; and a+b+c=4. Examples of aminosilanes that fit this formula areN-2-(aminoethyl)-3-aminopropyltrimethoxysilane,3-aminopropyltrimethoxysilane, 4-aminobutyltriethoxysilane,4-aminobutyldimethylmethoxysilane, and p-aminophenyltrimethoxysilane.The preferred silane is N-2-(aminoethyl)-3-aminopropyltrimethoxysilanehaving the formula:

    H.sub.2 N(CH.sub.2).sub.2 NH(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3

The hydrolyzed aminosilane is applied to the film as an aqueous solutionat any suitable stage during manufacture of the film, i.e., in-lineapplication, before or during the stretching operation, or it may alsobe applied after the stretching operation but prior to heat-setting thefilm. The resultant primed polyester film is found to exhibit adhesionto extrusion coated polymeric films.

It has been discovered that the application of the aqueous basedaminosilane primer coating to the polyester film after manufacturing thefilm, or to be more precise, after the polyester film has been heat setsuch that the majority of the film exists in a crystalline state, doesnot result in a primer coated polyester film having superior adhesioncharacteristics more suitable for direct extrusion coating with otherpolymers. Therefore, to obtain superior results, the aqueous basedaminosilane coatings of the present invention are applied before thepolyester film has been crystallized by heat setting, i.e., appliedin-line.

The primer formulation is prepared by mixing the aminosilane with waterat a level within the range of about 0.2 to about 6 percent by weight.Optionally a weak acid, such as acetic acid, may be added to facilitatehydrolysis. At least one of the hydrolyzeable groups of the silane ishydrolyzed into a silanol group (SiOH).

The preferred oriented polyester film for the purposes of this inventionis polyethylene terephthalate, although the invention is equallyapplicable to film based on a crystallizable polyester resulting fromthe polycondensation of a glycol such as ethylene glycol or butanediol,and mixtures thereof with terephthalic acid, or mixtures of terephthalicacid and other dicarboxylic acids such as isophthalic acid, diphenicacid and sebacic acid, or their polyester forming equivalents, whichpolyesters are made by methods well known in the art. The film may beproduced by techniques also well known in the art using well knownapparatus.

For example, the polyester is melted and extruded as an amorphous sheetonto a polished revolving casting drum to form a cast sheet of thepolymer. Thereafter, the film is stretched in one direction, either inthe direction of extrusion (longitudinal) or perpendicular to thedirection of extrusion (transverse) in the case of uniaxially orientedfilm, and in two directions in the case of biaxially oriented film, thatis, the film is stretched in both the longitudinal and transversedirections. The first stretching, to impart strength and toughness tothe film, can range from about 3.0 to about 5.0 times.

The hydrolyzed aminosilane primer coating of this invention in the formof an aqueous solution may be applied in-line at one of three stagesduring the film manufacture, namely; the pre-draw stage at the pointbetween the casting of the amorphous sheet and the first stretch such asdisclosed, for example, in British Pat. No. 1,411,564; the inter-drawstage subsequent to the uniaxial drawing but prior to biaxial drawingsuch as disclosed, for example, in the U.S. Pat. No. 4,214,035; or thepost draw stage subsequent to biaxial stretching, but prior toheat-setting the film. The primer is dried using conventional means suchas hot air dryers or infrared dryers, or a combination of both.

In a preferred embodiment, the primer coating is applied inter-draw,i.e., after the film is uniaxially stretched (after the film isstretched in one direction), but before the film is stretched in theorthogonal direction. In the preferred embodiment, the polyester film isfirst stretched in the longitudinal direction prior to coating. The filmis coated by any of the well known techniques employed in the art. Forexample, coating may be effected by roll coating, spray coating, slotcoating or immersion coating. In the preferred embodiment, the polyesterfilm is coated by means of gravure roll.

Corona discharge treatment decreases the hydrophobic character of thepolyester film surface, which permits the water based primer coating tomore easily wet the surface and thus improve the adhesion of the primercoating to the surface. The effect of the corona treatment is lost inthe heat setting step. So corona treatment is necessary to obtainwetting of the aminofunctional silane primer coating, but has nosignificant effect of the extrusion coated polymers to the polyesterfilm.

The hydrolyzed aminosilane of the present invention is applied to thefilm as an aqueous solution at a concentration of from about 0.2 toabout 6 percent by weight of the hydrolyzed aminosilane. A weak acidsuch as acetic acid may be added to facilitate hydrolysis. The preferredconcentration of the hydrolyzed aminosilane is within the range of about0.25 to 2.5 percent by weight. The preferred concentration is such toyield a final dry primer coating weight of from 1.0×10⁻³ g/m² to about4.0×10⁻² g/m² of film surface, and more preferably 2.0×10⁻³ g/m² to2.0×10⁻² g/m².

The coating of this invention may be applied to one or both sides of thefilm, or it may be applied to one side and a different coating such as athermosetting acrylic or methacrylic coating as taught in U.S. Pat. No.4,214,035 applied to the opposite side. The coating may also be appliedover a different primer coating to which it will adhere and which isalready present on the surface of the film, such as a thermosettingacrylic coating as described in U.S. Pat. No. 3,819,773.

The coating composition may also contain other ingredients so long assuch ingredients do not detract from the adhesion promoting action ofthe hydrolyzed aminosilane. Such would include minor amounts ofcolloidal silica, dyes, pH regulating agents, wetting agents, and thelike. The primer coating is present on the film surface as a continuouscoating, which term is also intended to include where the primer mayform a plurality of islands or segregated regions of coating.

Scrap film made during production that is coated with the primercoatings of this invention can be ground and mixed with fresh polyester,remelted, and reextruded to produce oriented films. Such film produced,containing significant quantities of primed scrap reclaim, exhibits verylittle degradation of physical properties due to the presence of thecoating impurity and color generation is also low. Thus the primed filmof this invention offers commercial advantage to the film manufacturerover many other primed films, such as films primed with vinylidenechloride containing polymers as disclosed in U.S. Pat. Nos. 2,627,088and 2,698,240, which tend to degrade and discolor when reclaimed as setforth above.

Laminates may be formed by the well known process of extrusion coatingwherein a molten sheet of polymer is continuously deposited on theprimer coated surface of a moving web of film. Laminates of polyesterwith polyethylene, ethylene-vinyl acetate copolymers, polyvinyl alcohol,polyvinyl acetate, and other polymers may be readily made by theextrusion coating process.

A film of PET which is extrusion coated with polyethylene hasparticularly useful properties such as good heat sealing capability oradhesion to other materials such as aluminum foil. Although theinventors are not certain, it is theorized that the amino group in theprimer reacts with the heated, oxidized polyethylene when it is extrudedonto the PET film, thus firmly bonding the primer to the polyethylene.

The thickness of polyester film suitable for use in this invention maygenerally range from about 0.25 to about 10 mils or more.

The following examples are illustrative of the invention:

FILM PREPARATION

N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS) (sold by DowCorning as Z-6020 and by Union Carbide as A-1120) orN-3-aminopropyltrimethoxysilane (APTMS) was dispersed in ordinary tapwater to form a concentration of from about 0.25 percent to 1.5 percentby Weight AE-APTMS (or other aminosilane, if indicated). Acetic acid wasadded at a concentration of 0.2 percent by weight to facilitatehydrolysis.

Polyethylene terephthalate polymer was melted and extruded through aslot die onto a casting drum maintained at a temperature of about 20° C.The melt solidified to form a cast sheet. The cast sheet waslongitudinally stretched at a draw ratio of approximately 3.5 to 1 whilemaintained at a temperature of about 80° C.

The longitudinally drawn film was corona treated by a corona dischargeapparatus and thereafter coated by reverse gravure with the solution ofhydrolyzed aminosilane prepared above.

The corona treated, longitudinally drawn, coated film was dried at atemperature of about 100° C. Thereafter, the film was stretched in thetransverse direction at a draw ratio of 3.9 to 1 to produce a biaxiallydrawn film. The thickness of the drawn film was from about 0.5 mils toabout 3 mils. The biaxially drawn film was then heat set at a maximumtemperature of 230° C.

Normally before extrusion coating the film as supplied by manufacturer,the raw film is corona treated and primed in a separate process stepprior to extrusion coating. The use of polyester film in-line coatedwith an aqueous based aminofunctional silane renders additional coronatreatment unnecessary. Corona treatment of the aminofunctional silaneprimed polyester film has no effect or a slightly negative effect on theadhesion of the extrusion coated polymer to the primed polyester film.

EXAMPLES 1-8

Polyethylene terephthalate film was made and coated as described in FILMPREPARATION and the film was 0.5 mil thick. The film was in-line coatedwith an aqueous coating of an amino silane as shown in Table 1. Acomposite roll was made containing 100 feet of film for each coatingformulation and the roll was run through an extrusion coater and coatedwith about 1 mil of low density polyethylene (LDPE) (USI resin with meltindex of 14). The melt temperature was 327° C. (620° F.) and the air gapwas approximately 8 inches. No additional corona treatment or primingwas used.

                  TABLE 1                                                         ______________________________________                                                   Coating                                                                       Formulation   Coating                                              Film       (% By Weight) Weight (g/m.sup.2)                                   ______________________________________                                        Example 1  Uncoated control                                                                            --                                                   Example 2  0.25% AE-APTMS*                                                                             1.3 × 10.sup.-3                                Example 3  0.5% AE APTMS*                                                                              2.6 × 10.sup.-3                                Example 4  1.0% AE-APTMS*                                                                              5.4 × 10.sup.-3                                Example 5  1.5% AE-APTMS*                                                                              8.0 × 10.sup.-3                                Example 6  0.5% APTMS**  2.0 × 10.sup.-3                                Example 7  1.0% APTMS**  4.0 × 10.sup.-3                                Example 8  1.5% APTMS**  6.0 × 10.sup.-3                                ______________________________________                                         *AE-APTMS is N2-(aminoethyl)-3-aminopropyltrimethoxysilane                    **APTMS is N3-aminopropyltrimethoxysilane                                

The adhesion of the low density polyethylene to the uncoated control ofExample 1 was 0.09 lbs./in. using ASTM tests D882 and E4. The adhesionof the low density polyethylene to the films of Examples 2-8 was so goodthat the two layers could not be separated in order to do a peel test.Separation at the PET/LDPE interface could not be achieved with hotwater, toluene, or tetrahydrofuran. Adhesion was excellent with bothAPTMS (N-3-aminopropyltrimethoxysilane) and AE-APTMS (N-2-aminoethyl)-3-aminopropyltrimethoxysilane).

EXAMPLES 9-28

Polyethylene terephthalate film was made and coated as described in FILMPREPARATION and the film was 0.5 mil thick. The film was in-line coatedwith an aqueous coating of an amino silane in a range of from 1×10⁻³g/m² to 3.0×10⁻² g/m². A composite roll Was made containing 100 feet offilm for each coating formulation and the roll was run through anextrusion coater and coated with about 0.75 mil of SURLYN® 1652, anionomer resin. The melt temperature was 307° C. (585° F.). Half of eachsample was corona treated a second time at 2.5 kVA prior to extrusioncoating and the other half was not corona treated a second time. Anothercomposite roll of the same film was coated with 0.75 mil of Norchem1014, a low density polyethylene resin, extruded at 330° C. (625° F.).As with the SURLYN®, half of each sample was corona treated and theother half was not. The peel strength was measured using an Instrontester. (During the extrusion coating operation strips of untreatedpolyester were inserted between the ends of the layers to provide anonadhered section where the two layers could be separated for the peeltest.)

The peel adhesion between the SURLYN® or LDPE, and the aminosilanecoated PET was measured on an Instron machine. A one inch wide strip wascut from the laminate and the two layers, either PET and SURLYN®, or PETand LDPE were separated at one end. The separated end of the PET wasinserted into the upper jaw of the Instron with approximately one inchdistance between the jaw and the point where the PET was still bonded tothe SURLYN® or LDPE. The free end of the SURLYN® or LDPE was insertedinto the lower jaw so that the strip was vertically aligned. The jawswere then moved away from one another and the force necessary to peelone layer from the other was recorded and reported in Table 2.

                  TABLE 2                                                         ______________________________________                                        Coating                                                                       Formulation            Adhesion(lbs./in.)                                     Film    (% By Weight) Corona   SURLYN  LDPE                                   ______________________________________                                        Example 9                                                                             0.25% AE-APTMS                                                                              YES      2.62    1.23                                   Example 10                                                                            0.25% AE-APTMS                                                                              NO       2.84    1.22                                   Example 11                                                                            0.50% AE-APTMS                                                                              YES      2.17    1.43                                   Example 12                                                                            0.50% AE-APTMS                                                                              NO       4.25    1.36                                   Example 13                                                                            1.00% AE-APTMS                                                                              YES      2.42    1.23                                   Example 14                                                                            1.00% AE-APTMS                                                                              NO       2.42    1.30                                   Example 15                                                                            1.50% AE-APTMS                                                                              YES      2.50    1.41                                   Example 16                                                                            1.50% AE-APTMS                                                                              NO       2.54    1.42                                   Example 17                                                                            0.25% APTMS   YES      3.19    1.28                                   Example 18                                                                            0.25% APTMS   NO       2.89    1.43                                   Example 19                                                                            0.50% APTMS   YES      2.24    1.25                                   Example 20                                                                            0.50% APTMS   NO       3.13    1.18                                   Example 21                                                                            1.00% APTMS   YES      1.58    1.23                                   Example 22                                                                            1.00% APTMS   NO       1.79    1.29                                   Example 23                                                                            1.50% APTMS   YES      1.94    1.67                                   Example 24                                                                            1.50% APTMS   NO       2.19    1.27                                   Example 25                                                                            Copolyester*  YES      1.03    0.44                                   Example 26                                                                            Copolyester*  NO       0.02    0.08                                   Example 27                                                                            Uncoated      YES      1.05    1.03                                   Example 28                                                                            Uncoated      NO       0.01    0.11                                   ______________________________________                                         *Film coated with a water dispersible copolyester coating described in        U.S. Pat. No. 4,493,872.                                                 

With the uncoated PET film and with the copolyester coated film, coronatreatment prior to extrusion coating is necessary to get some adhesionof the SURLYN® 1652 and Norchem® 1014 to the polyester film. Even withcorona treatment, adhesion to the uncoated PET and the copolyestercoated film was not as good as the aminosilane coated film. Also, asecond corona treatment of aminosilane coated film prior to extrusion ofthe SURLYN® or LDPE was not necessary and made little or no differencein the adhesion. Adhesion was good for both AE-APTMS and APTMS at aconcentration as low as 0.25 percent by weight.

EXAMPLE 29

The previous examples were all in-line primer coated film. This exampleand Example 30 compare in-line versus off-line coating.N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS) was dissolvedin deionized water to a concentration of 1.5 percent by weight ofAE-APTMS.

Polyethylene terephthalate polymer was melted and extruded as describedin Film Preparation. The longitudinally drawn film was corona treated bya corona discharge apparatus and thereafter coated by reverse gravurewith the solution of hydrolyzed aminosilane prepared above. The coronatreated, longitudinally drawn, coated film was dried at a temperature ofabout 100° C. Thereafter, the film was stretched in the transversedirection at a draw ratio of about 3.5 to 1 to produce a biaxially drawnfilm. The biaxially drawn film was then heat set at a maximumtemperature of 230° C. The dry weight of the coating was about 0.012g/m². The thickness of the base film was about 0.5 mil. (This process ofproducing a coated PET film is referred to as "in-line coating".)

The film, coated in-line with the aminosilane triol homopolymer, wasextrusion coated, without a second corona treatment, with Norchem® 1014low density polyethylene at 10 pounds/ream using an ER-WE-PAcoater/laminator. The LDPE was applied at an extrusion temperature of315° C. (600° F.), line speed of 200 fpm, and an air gap of 8 inches.

The experiment was repeated. The results are set forth in Table 3.

EXAMPLE 30

PET film was prepared as described in Film Preparation and in Example29, except that the film was not in-line coated with AE-APTMS. Thehydrolyzed AE-APTMS was applied to the PET film off-line in a separatecoating step on the ER-WE-PA coater/laminator using a 200 quad gravurecylinder in reverse mode. The coating weight was 0.10 g/m². The film wasthen extrusion coated with LDPE as described for Example 29.

The experiment was repeated. The results are set forth in Table 3.

The peel adhesion between the LDPE and the aminosilane coated PET forExamples 29 and 30 was as described with respect to Examples 9-28.

                  TABLE 3                                                         ______________________________________                                                      Coat Wt.  Bond Strength                                         ______________________________________                                        Example 29 In-Line  0.012 g/m.sup.2                                                                           1.40 lbs/inch                                 Repeat                          1.17                                                              Average =   1.28                                          Example 30 Off-Line 0.100 g/m.sup.2                                                                           0.60                                          Repeat                          0.54                                                              Average =   0.57                                          ______________________________________                                    

PET film, in-line coated with aminosilane as in Example 29, clearlygives superior adhesion to extrusion coated polymers compared with PEToff-line coated with aminosilane as in Example 30.

EXAMPLE 31

In the previous examples mono- and diamines were tested. In thisexample, a triamine was tested.

PET film was prepared and primed as described in Film Preparation,except that the aminosilane employed was N-2-aminoethyl-2aminoethyl-3-aminopropyltrimethoxysilane (AE-AE-APTMS) dissolved andhydrolyzed at a concentration of 0.50 percent, 1.0 percent and 1.5percent by weight in deionized water. The primed film was extrusioncoated with either SURLYN® 1652 resin or Norchem 1014 low densitypolyethylene (LDPE) as described with respect to Examples 9-28. Theadhesion was measured as described in Examples 9-28 and the results areset forth in Table 4.

                  TABLE 4                                                         ______________________________________                                                     g/m.sup.2                                                        % By Weight  Dry Coating Bond Strength (lbs/in)                               Coating Formulation                                                                        Weight      SURLYN ®                                                                             LDPE                                      ______________________________________                                         0.50        0.0098      2.25       1.20                                      1.0          0.0245      1.63       1.00                                      1.5          0.0353      1.17       1.38                                      ______________________________________                                    

The results show that triamines are good for primer coating PET film fordirect extrusion coating purposes.

Thus it is apparent that there has been provided, in accordance with theinvention, a primed film capable of being extrusion coated and anextrusion coated laminate that fully satisfies the objects, aims, andadvantages set forth above. While the invention has been described inconjunction with specific embodiments thereof, it is evident that manyalternatives, modifications, and variations will be apparent to thoseskilled in the art in light of the foregoing description. Accordingly,it is intended to embrace all such alternatives, modifications, andvariations as fall within the spirit and broad scope of the invention.

What is claimed is:
 1. An oriented polyester film having a primercoating composition on at least one side thereof, said primer coatingcomposition comprising the dried residue of a hydrolyzed aminosilanecompound having the formula in the unhydrolyzed state:

    (R.sup.1).sub.a Si(R.sup.2).sub.b (R.sup.3).sub.c

wherein R¹ is a functional group with at least one primary amino group,R² is a hydrolyzeable group selected from the group consisting of alower alkoxy group having 1-8 carbon atoms, C₁ to C₈, an acetoxy group,or a halide group, and R³ is a nonreactive, nonhydrolyzeable groupselected from the group consisting of a lower alkyl having 1-8 carbonatoms, or a phenyl group; with (a) being greater than or equal to 1; (b)being greater than or equal to 1; (c) being greater than or equal tozero, and with a+b+c=4, said primer coating composition being appliedin-line to said polyester film prior to heat setting said film at aweight effective to improve the adhesion of one or more extrusion coatedpolymers to said polyester film.
 2. The film of claim 1, wherein thehydrolyzeable group R² is an alkoxy, selected from the group of amethoxy or an ethoxy.
 3. The film of claim 1, wherein the aminofunctional group R¹ is selected from the group of a primary amino group,a diamine, or a triamine.
 4. The film of claim 1, wherein the saidaminosilane is selected from the group consistingofN-2-(aminoethyl)-3-aminopropyltrimethoxysilane,3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane andN-2-aminoethyl-2-aminoethyl-3-aminopropyltrimethoxysilane.
 5. The filmof claim 1, wherein said oriented polyester film is polyethyleneterephthalate.
 6. The film of claim 5, wherein said film is biaxiallyoriented polyethylene terephthalate.
 7. The film of claim 6, whereinsaid film is prepared by melt extruding a substantially amorphouspolyester film and thereafter orienting the film by stretching itsequentially in two directions and heat setting the film, said primercoating composition being applied to said film as an aqueous solutionprior to stretching the film in one direction, or subsequent tostretching in one direction but prior to stretching in a mutuallyperpendicular direction, or subsequent to stretching in two directions.8. The film of claim 7, wherein said film is subjected to a coronadischarge treatment prior to the application of said primer coatingcomposition.
 9. The film of claim 7, wherein said primer coatingcomposition is applied subsequent to stretching in one direction butprior to stretching in a mutually perpendicular direction.
 10. The filmof claim 7, wherein said primer coating composition is an aqueousdispersion of an aminosilane compound selected from the group consistingof N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,N-2-aminoethyl-2-aminoethyl-3-aminopropyltrimethoxysilane.
 11. The filmof claim 10, wherein said primer coating composition is present at aweight of from about 1.0×10⁻³ to about 4.0×10⁻² grams per square meterof film surface on a dry weight basis.
 12. The primed film of claim 1,having a layer of another polymer adhered to the primer coated surfaceof said primed film.
 13. The film of claim 12, wherein said polymer isextrusion coated onto the primed film.
 14. The film of claim 13, whereinthe extrusion coated polymer is a polyester or copolyester.
 15. The filmof claim 13, wherein the extrusion coated polymer is a polyolefin. 16.The film of claim 15, wherein the extrusion coated polymer is selectedfrom polyethylene or an ethylene copolymer.
 17. The film of claim 13,wherein said extrusion coated polymer is selected from the groupconsisting of an ionomer resin, ethylene vinyl acetate, polyvinylalcohol, or polyvinyl acetate.